This study summarizes gross and histologic observations in canine hearts studied after 24-hour preservation and orthotopic transplantation. BIBLIOGRAPHIC REFERENCE: Spray, T.L., Watson, D.C., and Roberts, W.C.: Morphology of Canine Hearts After 24-Hour Preservation and Orthotopic Transplantation. Journal of Thoracic and Cardiovascular Surgery. 73: 880-886, June 1977.